METHOD, TERMINAL, AND SYSTEM FOR ESTABLISHING PoC GROUP SESSION IN PoC SYSTEM

ABSTRACT

A method, a terminal, and a system for establishing a Push to Talk Over Cellular (PoC) group session in a PoC network based on session initiation information, such as information regarding presence of clients to be invited or session start-up time. According to the method, Universal Resource Indicator (URI) information regarding invitation and Information Reservation Service (IRS) parameters are set up in a PoC eXtensible markup language Document Management Server (XDMS), and a PoC server is requested to provide an IRS so that a session is established.

PRIORITY

This application is a Divisional Application of U.S. patent applicationSer. No. 11/637,278 filed in the U.S. Patent and Trademark Office onDec. 12, 2006 and this application claims priority to applications filedwith the Korean Intellectual Property Office on Dec. 12, 2005, assignedSerial No. 2005-122154, and filed on Dec. 11, 2006, assigned Serial No.2006-125787, the contents of each of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method, a terminal, and a system forestablishing a Push to Talk Over Cellular (PoC) group session in a PoCsystem. More particularly, the present invention relates to a method, aterminal, and a system for providing an Invitation Reservation Service(IRS) while interworking with a PoC eXtensible markup language DocumentManagement Server (XDMS).

2. Description of the Related Art

As a result of breakthroughs in mobile communication technology andextensive use of communication networks, a larger range of services andapplications are provided via mobile telephones. In addition to basiccommunication services, users are demanding more diversified services,including a positioning service, a multimedia service, and a Push toTalk (PTT) service. In particular, the PTT service supports variousadditional functions (e.g., instant messenger, condition indicator,etc.), as well as group and voice communication provided by conventionalwireless telegraphs or Trunked Radio Systems (TRSs).

Various efforts are being made in the industry to realize the concept ofPTT as a service based on mobile communication networks, i.e. PoCservice, and enact corresponding standards. One of the distinctionsbetween conventional mobile communication services and the PoC serviceis that, according to the latter, users can perform communication whilemoving between sessions, if necessary, because they belong to aplurality of sessions. The requirement that users must be able tocommunicate while moving through a plurality of sessions is described inPoC Regulation 1.0 of Open Mobile Alliance (OMA), an organizationregulating pertinent mobile communication services.

The PoC Regulation 1.0 provides that a PoC session is divided into aone-to-one PoC session and a group PoC session. Such a PoC session isinitiated when a PoC client transmits a session request message to a PoCserver. However, when all members of an ad hoc group session orprearranged group session want to participate in communication, thesession initiator must confirm one by one if all clients can communicateat that time. To this end, the PoC client must repeatedly subscribe toand check the presence information of corresponding clients. Suchrepeated check of presence information requires signaling via wirelessaccess networks. This increases the cost and wastes wireless resources.

In an attempt to solve this problem, it has been suggested to employ aSession Initiation Protocol (SIP) PUBLISH method to realizenetwork-based session initialization. According to this conventionaltechnique, a PoC terminal requests a PoC service to provide an IRS, andsession setup parameters are stored in the PoC server in response to therequest. As used herein, the IRS refers to a service, the session ofwhich is initiated from a network by presence information or othersession setup parameters.

The technique requires extension of the format of an eXtensible MarkupLanguage (XML) schema for a PoC service setting, as provided by PoCRegulation 1.0, and XML data is stored in the PoC server. Consideringthe characteristics of XML data, which requires dynamic access to storeddocuments and convenience in editing, storage of IRS data in the PoCserver may increase the load on the server during management of PoCsessions, e.g. when a number of PoC group sessions are established.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve theabove-mentioned problems occurring in the prior art, and an object ofthe present invention is to provide a method, a terminal, and a systemfor providing an IRS while interworking with a PoC XDMS so load on a PoCserver is reduced when a PoC system provides an IRS.

Another object of the present invention is to provide a method, aterminal, and a system for reducing the burden of signaling on a PoCserver and efficiently managing an XML document regarding an IRS byseparating the management of service parameters for an IRS from aprocess for requesting an IRS.

In order to accomplish these objects, there is provided a method forproviding an IRS to establish a PoC group session in a PoC system, themethod including setting up IRS-related information in a PoC XDMS by aPoC terminal, the IRS-related information defining a sessioninitialization condition; transmitting an IRS identification (ID) foridentifying the IRS-related information to the PoC terminal by the PoCXDMS; and requesting a PoC server to provide an IRS for sessioninitialization by using the IRS ID by the PoC terminal.

In accordance with another aspect of the present invention, there isprovided a system for establishing a PoC group session in a PoC system,the system including a PoC terminal; a PoC XDMS; and a PoC server,wherein the PoC terminal sets up IRS-related information in the PoCXDMS, the IRS-related information defining a session initializationcondition, and requests the PoC server to provide an IRS for sessioninitialization by using an IRS ID, the PoC XDMS transmits the IRS ID foridentifying the IRS-related information to the PoC terminal, and the PoCserver performs session initialization by using the IRS ID when an IRSrequest message is received.

In accordance with another aspect of the present invention, there isprovided a terminal for establishing a PoC group session in a PoCsystem, the terminal including a data transmission unit fortransmitting/receiving packet data to/from a PoC server; an XML DocumentManagement Client (XDMC) for transmitting IRS-related information to aPoC XDMS to set up an IRS parameter, the XDMC storing an IRS ID foridentifying the IRS parameter when the IRS ID is received form the PoCXDMS; a PoC client for requesting the PoC server to provide an IRS byusing the IRS ID at an IRS request; and a memory unit for storing theIRS ID received from the PoC XDMS.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 shows the construction of a conventional PoC system

FIG. 2 is a block diagram showing the operation of a conventional PoCserver

FIG. 3 shows a Controlling PoC Function (CF) block and Participating PoCFunction (PF) blocks of the PoC server shown in FIGS. 1 and. 2

FIG. 4 is a block diagram showing a system for providing an IRS whileinterworking with a PoC XDMS according to the present invention;

FIG. 5 shows the flow of signals between a PoC UE for providing an IRSand a PoC XDMS according to the present invention;

FIG. 6 is a flowchart showing steps for requesting a PoC server toprovide a PoC client with an IRS by using an IRS ID;

FIG. 7 shows an example of a message transmitted when an IRS isrequested in the course of FIG. 5; and

FIG. 8 shows an example of a message transmitted to a PoC server by aPoC client when an IRS is requested in the course of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription of the present invention, a detailed description of knownfunctions and configurations incorporated herein is omitted to avoidmaking the subject matter of the present invention unclear.

It will be assumed in the following description that the presentinvention is applied to a Push to Talk (PTT) system, particularly a PTTOver Cellular (PoC) system for providing a PTT service via a cellularmobile communication network. In general, a PoC system employs anSession Initiation Protocol (SIP) and an extended SIP to transmitsession participation information for group communication, as well as aneXtensible Markup Language (XML) Configuration Access Protocol (XCAP) toobtain group information. These protocols are used to realize functionsof the present invention, as will be described below, and the basicstructure of the present invention is grounded by a PoC Regulation 1.0system.

The present invention is directed to a method and a system forefficiently providing an IRS while interworking with a PoC XDMS when anIRS is provided in an Open Mobile Alliance (OMA) PoC system.

A conventional PoC system, to which the present invention is applicable,will now be described.

FIG. 1 shows a conventional PoC system and a relevant network structure.This PoC system includes a PoC User Equipment (UE) or Terminal 100, XMLDocument Management Servers (XDMSs) 130 and 140, and a PoC server 150.The PoC system may further include an aggregation proxy server 160.These components are connected to one another via an access network 110,a Session Initiation Protocol/Internet Protocol (SIP/IP) core network120, and a remote PoC network 170.

Respective components will now be described.

The PoC UE 100 includes a PoC client 102 and an XML Document ManagementClient (XDMC) 104.

The PoC client 102 is incorporated in the PoC UE 100 as a servicerequester. Particularly, the PoC client 102 resides in the PoC UE 100and performs network access so a PoC service subscriber is provided witha PoC service via the PoC UE 100. In the following description, the term“PoC client” will collectively refer to a UE incorporating the same anda PoC service subscriber, and its reference will be omitted unlessotherwise noted.

The PoC client is mainly used to enable a PoC service subscriber (i.e.,a PoC user) to establish a PoC session, participate an alreadyestablished session, or terminate an established session. The PoC clientalso has the functions for creating and transmitting a talk burst,supporting an instant personal alert, and authenticating an access to aPoC service. The PoC client is connected to the SIP/IP core network 120,which plays a crucial role in supporting SIP/IP multimedia services, viathe access network 110.

The SIP/IP core network 120 is connected to the PoC server 150 and theXDMSs 130 and 140 to provide a PoC service. The PoC server 150 has a“controlling PoC” function for maintaining and managing PoC sessions anda “participating PoC” function for participating in a PoC sessionestablished for unilateral or multilateral communication.

Meanwhile, a PoC service may be followed by a group session setupservice, such as conference communication. To this end, OMA standardsdefine an XML Document Management Client (XDMC) 104 and XDMSs 130 and140 for a group list service. FIG. 1 shows a PoC XDMS 140 dedicated to aPoC service and a common XDMS 130 compatible with other serviceenablers. Information regarding groups and group members is inputted tothe XDMSs 130 and 140 via the PoC client. From a list of individuals orgroups received from the XDMSs 130 and 140, the PoC client obtainsinformation regarding PoC clients it can call. Creation, modification,and management of groups and group members regarding the XDMSs 130 and140 may be conducted via a communication network, which can be relied onby PoC service providers, such as Internet or intranet. Furtherdescription of protocols for managing XML documents (e.g. creation,modification, and removal of group lists) will be omitted for clarity.

Upon receiving a request regarding group lists from the XDMC 104 duringa group service, the aggregation proxy server 160 routes it torespective XDMSs 130 and 140 according to a suitable rule.

The PoC server 150 will now be described.

FIG. 2 shows a conventional PoC server 150. The functionality of the PoCserver 150 may be divided into a “Controlling PoC Function”(hereinafter, referred to as CF) for maintaining and managing PoCsessions on a broad scale and a “Participating PoC Function”(hereinafter, referred to as PF) for maintaining and managing respectivesessions. Functional characteristics of the PoC server will now bedescribed with reference to Tables 1 and 2 given below.

TABLE 1 Controlling PoC Function (CF) Provides centralized PoC sessionhandling Provides the centralized Media distribution Provides thecentralized Talk Burst Arbitration functionality including talkeridentification Provides SIP session handling, such as SIP sessionorigination, termination, etc. Provides policy enforcement forparticipation in group sessions Provides the participants informationCollects and provides centralized media quality information Providescentralized charging reports May provide transcoding between differentcodecs Support Talk Burst Control Protocol Negotiation

Among the functionality of the PoC server 150, the CF is related to theoverall management of PoC sessions, as shown in Table 1. Particularly,the CF sanctions PoC clients' request for a floor, decides the order,and empowers them. When a PoC client requests a talk burst, it isdistributed to other PoC clients participating in the same groupcalling. In addition, information regarding PoC clients participating inthe group calling is provided.

The PF is related to the management of sessions linked with the CF andrespective PoC clients during a PoC session, as shown in following Table2. Particularly, the PF relays a PoC client's request for a floor, aswell as a grant of a floor to the PoC client by the CF. In addition, thePF relays media between the CF and PoC clients and, if differentcoder/decoders (codecs) are used between them, the PF transcodes them.When a talk begins in a session while another talk is going on in adifferent session (i.e., during a simultaneous session), one of them isfiltered based on the PoC user's selection.

TABLE 2 Participating PoC Function (PF) Provides PoC session handlingMay provide the Media relay function between PoC Client and ControllingPoC server May provide user media adaptation procedures May provide TalkBurst control message relay function PoC Client and Controlling PoCserver Provides SIP session handling, such as SIP session origination,termination, etc., on behalf of the represented PoC Client Providespolicy enforcement for incoming PoC session (e.g. access control,incoming PoC session barring, availability status, etc.) May collect andprovide media quality information Provides the participant chargingreports May provide filtering of the media streams in the case ofsimultaneous sessions May provide transcoding between different codecsMay support Talk Burst Control Protocol Negotiation Stores the currentAnswer Mode and Incoming PoC Session Barring preferences of the PoCClient

FIG. 3 shows a CF block and PF blocks of the PoC server 150 shown inFIGS. 1 and 2.

Referring to FIG. 3, respective PoC clients 102-A to 102-D access a CFblock 300 via PF blocks 310-A to 310-D and set up a PoC session. The CFblock 300 endows the PoC clients with a floor, and their mediacorresponding to the floor are transmitted to respective PoC clients.Even though endowed with the floor, the PoC clients cannot take thefloor until they check information regarding PoC clients participatingin the group session.

Meanwhile, call processing technology for communication connection in aPoC system may have various procedures depending on requirements andconditions of transmission and reception sides. Characteristics of a PoCsystem used by such setups of the transmission and reception sides,based on OMA, will now be described.

The reception side can select its response mode from automatic andmanual response modes at the request of a PoC client. In the automaticresponse mode, a response is directly sent to the transmission side by acorresponding network, instead of the receiver's manual response, whenthe transmission side is included in a PoC client list prepared by thereception side. Such an automatic response sent by the network withoutoperating a terminal is based on the fact that the PoC server can storeinformation regarding the response mode and a corresponding user list inaccordance with a response mode setup request of the terminal. In themanual response mode, particularly, when the transmission side is notincluded in the automatic response user list, when it is unclear if thetransmission side is included in the list or not, or when the receiverwants manual response to every user, a PoC communication request istransmitted to the terminal via the reception network so that the callis connected after the PoC client's permission.

The PoC system may enter into an on-demand session mode or a preestablished session mode depending on the connection setup to a PoCserver in the user's home network. In the pre-established session mode,a session is pre-established by a PoC client as desired between him anda PoC server belonging to his home network. The pre-established sessionis necessary to negotiate a media parameter to be used by a PoC clientwith the PoC server in advance so that a session can be establishedrapidly without repeatedly negotiating a media parameter between the PoCserver and the client for future use.

In order to set up a prior session, a PoC client employs an SIP methodto provide a media parameter supporting a body, particularly an SessionDescription Protocol Multipurpose Internet Mail Extensions (SDP MIME)body. The PoC client provides a media parameter, which has been receivedfrom the server, and responds to the media parameter. Upon receiving aresponse message from the server, the PoC client inserts identificationinformation of a newly established prior session, particularlyconference URI, and sends it to the PoC client.

When the prior session is used, it is possible to negotiate in advancean IP address, a port number, a codec to be used, and a talk burstcontrol protocol. The on-demand session mode corresponds to a case inwhich no prior session has been set up by any PoC client. This meansthat a procedure for connecting a PoC call is performed after aninvitation message is received from another PoC client.

The setup of a response mode with regard to a communication request in aPoC system can be stored in both a PoC server, which is a networkelement, and a PoC client, which is a terminal.

When a response mode is set up in a home network managing a PoC client,the response mode is realized in a PoC server having a PF in the networkto which the PoC client belongs.

When a response mode has been set up in a network, the PF automaticallyresponds to another PoC server's request for PoC communication bytransmitting a session progress message to the network, which hasrequested communication. Therefore, in the automatic response mode, thecommunication request procedure is simpler than in the case of aresponse after transmission of a session setup message to the PoCclient. This reduces the time for initially granting a floor.

When the network responds automatically, the result may differ from theuser's intention, depending on the situation. Therefore, a PoC clientmay have its own response mode setup, which is preferential over that ofthe network. This is for the purpose of avoiding a privacy problemoccurring when a PoC client modifies its response mode and requests thePoC server to update the response mode, but the response mode is notupdated in real time due to signal delay or error in the network.

In summary, although a user can set up a response mode for both a PoCserver and a PoC client in the case of a PoC service, the response modesetup of the PoC client reflects the user's latest intention. Therefore,a decision is made based on the response mode for the PoC client when astream of media (e.g. user's actual voice or image) is transmitted.

A procedure for establishing a PoC multimedia session in a PoC system,which has the above-mentioned characteristics, will now be described.

A transmission-side PoC client uses an SIP protocol and transmits amessage for inviting a multimedia, including various formats of audio,video, and texts depending on a designated media type, in order torequest call processing. In response to the call processing request, areception-side client follows various responding procedures inaccordance with a response mode setup in the corresponding PoC serverand a prior session, if any. An example of a procedure for processing acall for PoC communication will now be described in the case oftransmission-side and reception-side networks, respectively.

A transmission-side PoC client sends an SIP invitation request, whichinclude information regarding the SIP address of a desiredreception-side PoC client, to a corresponding SIP/IP core network. TheSIP invitation message may further include information regarding the PoCaddress of the transmission-side PoC client, requested media parameters,and information regarding a characteristic value indicating a PoCservice. The requested media parameters may include a number ofcharacteristic values indicating, for example, an encoding methodregarding audio and video, a rate, a payload type, etc., when amultimedia session is requested.

The SIP invitation message is transmitted to a PF server via acorresponding IMS server in an IMS network, particularly via Proxy CallSession Control Function (P-CSCF) and Serving Call Session ControlFunction(S-CSCF), based on a path query in a Dynamic Host ConfigurationProtocol (DHCP) server or Domain Name Server (DNS) server. In the caseof a normal communication request, a PF server, to which a PoC client isconnected, may be realized to be separate from a CF server for managingthe talk burst of an established session. Therefore, the SIP invitationrequest, which has been sent to the PF server, is transmitted to the CFserver via an SIP/IP core network of a corresponding network.

A PoC session control network incorporating a CF transmits the SIPinvitation message to the reception-side network and receives a responsemessage from the reception-side network. Depending on the reception-sidePoC client and PF setup, the SIP response message from thereception-side network may contain a provisional response (1xx), asuccessful response (2x), or an erroneous response (4xx-6xx). In thecase of an automatic response mode, an SIP 183 “session progress” signalmay be received as a response message, which is used to connect the PoCserver and the client in the IMS network of the communication requester.As a communication permission signal of the reception-side PoC client,an SIP 183 “session progress” or SIP 200 “OK” response is transmitted tothe PoC client via CF and PF PoC servers. Upon receiving the SIP 183“session progress” or SIP 200 “OK” signal from the reception-side PoCserver, the CF confirms that the PoC call has been connected andtransmits a floor grant signal to the transmission-side PoC client so atalk burst floor is granted. The response to the SIP 183 “sessionprogress” or SIP 200 “OK” signal, i.e. a response regarding the talkburst floor is either “confirmed” or “unconfirmed”. When the CF receivesthe “unconfirmed” response, it uses a buffering function.

Upon receiving a response signal to the SIP invitation request signal,the transmission-side PoC client receives a signal for permitting talkburst transmission, e.g., a floor grant signal for transmitting a ringback tone, via an RTCP protocol. The floor grant signal is created by aCF authorized to mediate talk burst and is transmitted to a PoC clientvia a PF managing the corresponding PoC client. The floor grant signalmay bypass an SIP/IP core network (e.g. IMS), because a bearer path, notan SIP protocol, is used. After confirming the ring back tone, the PoCclient transmits a voice stream by using an Real-time Transport Protocol(RTP), for example.

A system for establishing a PoC group session in a PoC system, which isconstructed as mentioned above, while interworking with a PoC XDMS willnow be described with reference to FIG. 4, which shows a system forproviding an IRS while interworking with a PoC XDMS according to thepresent invention.

Referring to FIG. 4, the inventive system includes a PoC UE 400, a PoCXDMS 420, and a PoC server 430. The PoC UE 400 is connectible to the PoCXDMS 420 via an IP network 406 and an aggregation proxy server 410. ThePoC UE 400 is also connectible to the PoC server 430 via the IP network406 and an IMS core network 407.

The PoC UE 400 includes a control unit for controlling the overalloperation of the UE; a PoC client 402 for processing an SIP protocolused to establish and manage PoC sessions; an XDMS 401 for managing XMLdocuments used for PoC services; a memory unit 403 for storinginformation regarding the address and group of PoC clients, as well asinformation regarding the IRS proposed by the present invention; a userinterface 404; and a data transmission unit 405. The user interface 404transmits the user's input to the PoC UE 400. The data transmission unit405 transmits/receives packet data. To this end, the data transmissionunit 405 may include transmission protocol stacks, e.g. RTP/RTP ControlProtocol (RTCP)/HyperText Transfer Protocol (HTTP) (RTP/RTCP/HTTP), UPD,IP, and lower layer stacks.

The PoC client 402 establishes a session at the user's request by meansof the user interface 404 and, when Uniform Resource Identifier (URI)information or group URI information stored in the memory 403 isnecessary, retrieves address information while interworking with theXDMC 401 inside the UE. The memory 403 inside the UE manages URI listinformation as an XML document. The memory 403 may also storeIRS-related information, which is stored in the PoC XDMS 402 by the XDMS401, by using the same IRS ID.

Steps for storing IRS-related information in the PoC XDMS 420 by theXDMS inside the PoC UE 400 and receiving an IRS ID from the PoC XDMS 420will now be described with reference to FIG. 5, which shows the flow ofsignals between a PoC UE for providing an IRS and a PoC XDMS accordingto the present invention.

The XDMC 401 inside the UE creates an IRS parameter wanted by the user.The IRS parameter may include at least one of the following informationto initiate session by PoC Server, comprising e.g., the minimum numberof PoC clients that can be invited, answer mode of the invited PoCclient, PoC service registration status of the invited PoC client, thepresence information type for session initiation, the session initiationtime, the session request triggering condition, and the expiration timeof the IRS request.

The XDMC 401 uses an XCAP protocol and transmits an HTTP PUT message,including the created IRS parameter and URI information for sessionsetup, to the PoC XDMS 420 in steps 500 and 502. The XCAP enables easyaccess to and editing of XML documents. The created IRS parameter istransmitted to the aggregation proxy server 410 by using the HTTP PUTmessage. The aggregation proxy server 410 performs authentication,compression, and routing of requested messages. Particularly, theaggregation proxy server 410 forwards messages to the PoC XDMS 420,which is the destination of corresponding XML documents. As mentionedabove, the transmitted HTTP PUT message may include URI list or groupURI information, to which an IRS is to be applied, as well as IRSparameters. Target URI information is transmitted together with a PoCIRS session initiation condition, particularly an IRS parameter. The IRSID included in the response is used to identify a list setup and an IRSparameter.

After receiving the message, the PoC XDMS 420 stores the IRS-relatedparameter included in the received message. An IRS ID for mapping theIRS parameter is created and transmitted to the corresponding XDMC 401via the aggregation proxy server 410, while being included in a responsemessage, in steps 504 and 506. The XDMC 401 may selectively store thereceived IRS ID in the memory unit 403 in step 508. Although the presentembodiment has been described on an assumption that the XDMC requeststhe PoC XDMS to provide a service parameter and that the PoC XDMScreates an IRS ID in response to the request and transmits it to theXDMS, the XDMC may create the IRS ID by itself. In this case, the XDMChas to neither receive an IRS ID, which has been mapped by the PoC XDMS,nor initiate a session.

As such, the process of setting up IRS-related information for defininga condition for initiating a network-based session between the XDMC 401inside the PoC UE 400 and the PoC XDMS 420 includestransmission/reception of an IRS parameter, which acts as a sessioninitiation condition of a PoC IRS, and an IRS ID for identifying an IRSparameter setup.

An example of an HTTP PUT message transmitted from the XDMC 401 to thePoC XDMS 420 in the course of FIG. 5 will now be described withreference to FIG. 7, which shows an XML document type of an IRSparameter to be transmitted to the PoC XDMS 420 by the XDMC 401. Thebody of the HTTP PUT message includes a field value of “irs-setting”,which indicates an XML document newly defined for an IRS, a sub-fieldvalue of “irs-params” for an IRS parameter, and “resource-list”indicating target URI information. The field value of “irs-params”consists of session start-up time, presence information, and reservationexpiration time. The field value of “resource-list” consists of a UIRlist or group URI information representing it.

As mentioned above, according to the present invention, the PoC UE 400pre-stores IRS information, such as URI information regarding invitationfor session establishment and an IRS parameter, in the PoC XDMS 420 viathe XDMC 401. Based on the stored information, the PoC UE 400 receivesan ID from the PoC XDMS 420, which provides an IRS mapped onto thestored information.

Upon receiving the user's input for requesting an IRS, the PoC client402 of the PoC UE 400 uses the IRS ID and requests the PoC server 430 toprovide an IRS so that a session is established. FIG. 6 shows steps forrequesting a PoC server to provide a PoC client with an IRS by using anIRS ID according to the present invention.

The PoC client 402 transmits a message for requesting an IRS ID to theXDMC 401 inside the UE in order to request an IRS. Upon receiving themessage, the XDMC 401 retrieves an IRS ID in step 602. The XDMC 401transmits the retrieved IRS ID to the PoC client 402 in step 604.Instead of obtaining the IRS ID directly from the PoC XDMS 420 by usingan XDMC function, as has been described with reference to FIG. 5, an IRSID stored in the memory unit 403 may be used. The IRS ID transmissionprocess may also be realized by specific internal signaling between thePoC client 402 and the XDMC 401. Specifically, the step of retrievingthe IRS ID at the request of the PoC client 402 may include at least oneof a step of retrieving XML data inside the PoC XDMS 420 and a step ofretrieving the IRS ID from the memory unit 402 inside the UE, the memoryunit 402 storing XML data while being synchronized with the PoC XDMSserver.

The PoC client 402 transmits the received IRS ID and a message forrequesting an IRS to the PoC client 430 in the home network via anSIP/IP core network in steps 606 and 608. The message for requesting anIRS may be an SIP PUBLISH message, and the PoC service setting valueincluded in the SIP PUBLISH message may be used to designate a fieldvalue of “IRS” and announce if the IRS is applied or not. For example,when the field value is “on”, the IRS is requested and, when the fieldvalue is “off”, the IRS is not requested.

The IRS request message already includes URI list information in theprocess of issuing an IRS ID, as shown in FIG. 5. Therefore, it isunnecessary to insert target URI information inserted into the PUBLISHmessage. If an IRS ID has been issued instead of target URI informationin the course of FIG. 5, it is necessary to insert correspondinginformation, i.e., a URI list or group URI, into the SDP body portion ofthe IRS request message in the course of FIG. 6.

After receiving the IRS ID and the IRS request message from the PoCclient 402 in step 608, the PoC server 430 transmits a subscriptionrequest message for subscribing to information, which is necessary toprovide an IRS, to the PoC XDMS 420 in step 614. The subscriptionrequest message includes the IRS ID received from the PoC client 402 andis used to subscribe to IRS-related information (e.g., target URIinformation stored while being mapped onto the IRS ID, IRS parameters)provided by the PoC XDMS 420.

After receiving the subscription request message, the PoC XDMS 420transmits a response message to the PoC server 430 in step 616 andtransmits the IRS-related information stored while being mapped onto thereceived IRS ID, particularly the target URI information and IRSparameters, to the PoC server 430 in step 618. Upon receiving theIRS-related information, the PoC server 430 transmits a response messageto the PoC XDMS 620 in step 620. The PoC server 430 evaluates theservice condition in step 622 and, if the evaluated service condition isacceptable, initializes the session in step 624. Depending on ifpresence information is included or not, the PoC server 430 mayinterwork with the presence server in the process of receiving the IRSparameter from the PoC XDMS 420 by means of the IRS ID and establishinga group session in accordance with the service condition.

The SIP PUBLISH message, which is used by the PoC client 402 to requestthe PoC server 430 to provide an IRS in the course of FIG. 6, will nowbe described with reference to FIG. 8, which shows an example of the SIPPUBLISH message.

Generally, the SIP PUBLISH message extends the PoC service setting,which is defined by PoCl, and includes “irs-service” element. Dependingon the value of “true” or “false, it is decided if an IRS is requestedor not. The SIP PUBLISH message also includes “irs-id” element, which isused by the PoC server 430 to retrieve the requested IRS parameter fromthe PoC XDMS 420, and which may be indicated by a binary number.

Realization of the extended SIP PUBLISH message requires definition ofan XML schema. However, definition of the schema falls out of the scopeof the present invention, and further description thereof will beomitted herein.

In summary, the present invention provides a PoC XDMS-interworking IRS,as shown in FIG. 5, by setting an IRS parameter for defining anetwork-based session initialization condition between the XDMC 401inside the PoC UE 400 and the PoC XDMS 420. Based on the parametersetup, the PoC UR 400 receives an IRS ID from the responding PoC XDMS420. As shown in FIG. 6, the PoC client 402 retrieves the stored IRS IDat the IRS request and transmits a message for requests an IRScorresponding to the IRS ID to the PoC server. Upon receiving themessage, the PoC server 420 receives an IRS parameter, which has beenmapped onto the IRS ID, from the PoC XDMS 420 and establishes a sessionif the service condition is satisfied.

The network element for storing IRS service parameter is not limited toPoC XDMS, and the other element of the network for providing a PoCservice can be used. Therefore, a Shared XDMS or newly defined IRSservice storage for storing the same service parameter may be used. Evenwhen the network construction such as the above is changed, the contentsof same service parameter and the flow of signal as described in thepresent invention can be applied.

As mentioned above, the present invention has the advantage of a reducedburden of signaling on the PoC server, which manages PoC sessions, bydividing the method for providing an IRS by initiating a session basedon the network into a process for setting up an IRS parameter and aprocess for requesting a service, when various conditions for sessionestablishment are satisfied. In addition, relevant XML data can bemanaged more dynamically by creating, modifying, and deleting IRSparameters in the same manner as target URI list information.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

1. A method for providing an Invitation Reservation Service (IRS) usingSession Initiation Protocol (SIP)/Internet Protocol(IP) core networks ina server, the method comprising the steps of receiving IRS-relatedinformation defining a session initialization condition from a terminalfor requesting session initiation; storing the IRS-related informationand mapping information of the IRS-related information by interworkingwith the terminal; and receiving a request for providing the IRS-relatedinformation corresponding to the mapping information and providing theIRS-related information to the terminal.
 2. The method as claimed inclaim 1, wherein storing the IRS-related information and mappinginformation of the IRS-related information comprises: generating themapping information of the IRS-related information and the mappinginformation; and transmitting the mapping information to the terminaland requesting the terminal to store the mapping information.
 3. Themethod as claimed in claim 2, wherein the mapping information of theIRS-related information comprises an IRS Identifier (ID) for identifyingthe IRS-related information stored in the server.
 4. The method asclaimed in claim 1, wherein receiving the IRS-related informationfurther comprises receiving mapping information of the IRS-relatedinformation stored in a memory unit of the terminal; and wherein storingthe IRS-related information comprises storing the IRS-relatedinformation and mapping information received from the terminal in theserver.